Motor/pump unit, especially for antislip brake systems

ABSTRACT

The present invention relates to a motor/pump unit, especially for slip-controlled motor vehicle brake systems, including an accommodating member for hydraulically active components, an internal gear pump arranged in a bore of the accommodating member and comprising pump components such as a pinion/internal gear combination arranged between two housing parts, wherein the pump components form a pre-assembled unit, and including a motor for driving the internal gear pump. An object of the invention is to devise a motor/pump unit, which allows a space-saving and low-cost integration of an internal gear pump in an accommodating member. This object is achieved in that the housing parts can be arranged preliminarily by at least one securing element in such a fashion that the final alignment of the housing parts relative to each other takes place when the unit is inserted into the accommodating member.

TECHNICAL FIELD

The present invention relates to a motor/pump unit, especially forslip-controlled motor vehicle brake systems, including the features ofthe preamble of patent claim 1.

BACKGROUND OF THE INVENTION

Electronically controllable motor vehicle brake systems including apressure-generating device configured as a piston pump for generatinghydraulic pressure and a motor for this purpose are principally known inthe art. A piston pump of the eccentric type necessitates at least twoangularly arranged bores to accommodate a driving shaft and at least onepump piston. At least one pressure valve and one suction valve arenecessary for the charge changing. This type of pump suffers from thebasic and constructively induced shortcoming that inevitable and audiblepressure pulsations develop during fluid delivery. The running noise isprincipally tolerated because the pump of conventional, slip-controlledbrake systems is switched on only rarely in average driving operations,for example, when a brake slip limit or a traction slip limit isexceeded. However, so-called electrohydraulic brake systems (EHB)require longer pump running periods because the pump is used to charge apressure accumulator generally serving for the hydraulic pressureincrease in wheel brakes during brake applications. An extension of thepump running period may also be related thereto when the pump—withoutusing a pressure accumulator—is used for the direct pressure increase inwheel brakes. Admittedly, measures are known to improve the noisebehavior, e.g. pumps are known including three or more pistons causinglower pulsations in total. Nevertheless, the comfort behavior isregarded as being in need of improvement.

DE 199 18 390 A1 discloses a vehicle brake device with a two-circuitinternal gear pump. The internal gear pump can be inserted as a unitinto an accommodating member. For this purpose, the internal gear pumpcomprises several disc-shaped housing parts of equal diameter that abuton each other axially in addition to pinion/internal gear assemblies.Said housing parts are aligned relative to each other and welded attheir periphery before the pump is inserted into the essentiallycylindrical bore in the accommodating member. The highly accuratealignment and fixation of the housing parts is complicated and costly.

DE 100 04 518 A1 discloses an internal gear pump designed as a cartridgeand including an essentially bowl-shaped first housing part whichaccommodates a pinion shaft, an internal gear, and a second housingpart. The second housing part is centered in the first housing part,which in turn is inserted into a stepped-diameter bore of theaccommodating member and secured thereto. This arrangement allowstesting the cartridge separately. Nevertheless, the structural effort isconsidered as too high.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to devise a motor/pump unit, whichavoids the shortcomings of the state of the art and allows aspace-saving and low-cost integration of an internal gear pump in anaccommodating member.

According to the invention, this object is achieved in that the housingparts can be arranged preliminarily on each other by at least onesecuring element in such a fashion that the final alignment of thehousing parts relative to each other takes place when the unit isinserted into the accommodating member. According to the invention, thealignment of the pump components grouped as a unit is carried out quasiautomatically upon insertion into the accommodating member. Thisobviates the need for the working steps relating to the alignment oradjustment. A separate cartridge for the pump is omitted. Nevertheless,the internal gear pump can be fitted for testing purposes into a testingdevice, the design of which corresponds largely with the design of theaccommodating member.

In a favorable embodiment of the invention, the at least one securingelement connects the housing parts with a relative clearance to eachother, and a bore is provided in the accommodating member for the finalalignment of the housing parts in a radial direction. This provisionwill safeguard that the internal gear pump can be integrated in theaccommodating member, while double fits, cumulative tolerances, orsimilar conditions are avoided.

Further, in an advantageous aspect of the invention, a first housingpart is fixed on the accommodating member so as to be undisplaceable inan axial direction and a radial direction and, in addition, is used tolock the pump components in the accommodating member. Consequently, thefirst housing part additionally fulfils a locking function for at leastone other pump component, what limits the structural effort.

A pin with a first end can be provided as a securing element which ispress fitted into a bore of the first housing part, said pin including asecond end with a stop for securing the second housing part in position.The reverse arrangement is likewise possible.

For a simple assembly in an axial direction it is favorable that the pinis arranged in parallel to a pump shaft. Furthermore, for a simpledesign the pin includes a cylindrical portion, which extends through abore of the stop-sided housing part, with the bore in this housing parthaving a larger diameter compared to the cylindrical portion, and withthe diameter being smaller compared to the stop. This permits aform-locking pre-assembly of the unit without causing tension during theinsertion into the accommodating member.

Up to three pins are provided for a safe and statically definedpre-assembly, said pins being evenly distributed over the periphery,that means they are arranged at a regular angle relative to each other.

To permit a compensation of the distances of the tips of teeth, it isfavorable that the internal gear is supported in a ring, said ring beingarranged in an axial direction between the housing parts, and said ringbeing pivotable relative to the housing parts about a pivot axis that isarranged in parallel to the pump shaft.

To allow an elastic preload of the ring, a housing part accommodates anend of a spring element, while another free end of the spring element isengaged in a bore of the ring under elastic deformation, especiallysubjected to bending. The result is that the spring elements causeelastic preload between internal gear and pinion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged cross-sectional view of an internal gear pump fromobliquely above.

FIG. 2 is a cross-sectional view of an internal gear pump according toFIG. 1 from obliquely below.

FIG. 3 is a cross-sectional view of a motor/pump unit.

FIG. 4 is an enlarged view showing details of an internal gear pump likein FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to a motor/pump unit 1, as shown in FIG. 3, whichcomprises an electric motor 2 that is attached to an accommodatingmember 3 for hydraulically active components, such as especiallyelectromagnetically operable valves, accumulator chambers, and channelsinterconnecting these components. Motor 2 comprises a bowl-shaped motorhousing that is covered at the end by an end plate 4, which ispreferably made of plastic material and used for the temporaryaccommodation of a bearing 5. Said accommodation does not serve to carryoff bearing forces during operation of the motor/pump unit 1 but onlyfor a pre-assembly of structural components so that the motor 2 alongwith a provisionally supported driving shaft 6 can be tested as aseparate modular unit. With the bearing 5, the driving shaft 6 issupported in a bore 7 close to the accommodating member to accommodate apump 8. Pump 8 is configured as an internal gear pump and includes asupply channel 9 for the connection of a pressure fluid reservoir suchas, in particular, a brake fluid tank, a master cylinder or a simulatorwith a separable displacement chamber 10, as well as a discharge channel11 leading from the displacement chamber 10 in the direction of at leastone pressure fluid consumer, such as a pressure fluid accumulator and/orwheel brakes. A pinion 13 is arranged at a pump shaft 12 in anunrotatable fashion. The connection is carried out by means of a pressfit or a shrinking operation. For driving purposes, the pump shaft 12 iscoupled to the driving shaft 6 in the area of freely protruding pivots14, 15 by means of a separate shaft coupling. It is, however, possibleto interconnect the two shaft ends directly by a corresponding design,that means without a separate shaft coupling. Due to a rotatingentrainment, the pinion 13 meshes with an internal gear 16 that isembraced by a ring 17 (compensation ring) for the mounting support.Pinion 13 comprises a smaller number of teeth than the internal gear 16.For example, a difference of one tooth is provided. The internal gear 16is arranged eccentrically in relation to the pinion 13. The meshing ofthe pinion-internal gear combination causes inlet-side tooth gaps to befilled with the medium being pumped, in particular brake fluid. On theone hand, there is a sealing effect between abutting tooth edges and, onthe other hand, a sealing effect between abutting tooth heads so that asuction area is separated from a pressure area, and displacement takesplace in such a way that the medium is pressed out at the outlet sidefor pressure increase. A bearing 18, preferably a sliding bearing oralternatively a roller bearing, in particular a needle ring asillustrated in FIGS. 1 and 2, is used to support the internal gear 16 inthe ring 17 in a radial direction. To reduce the surface pressure thatacts on the internal gear 16, an outside periphery facing the bearingcan be enlarged compared to a toothing area corresponding to FIG. 4. Tocompensate tooth head distances, the ring 17 is pivotal within certainlimits about a pivot axis A in the form of a pin 46 so that in the pumpoperation a portion of ring 17 that lies in a mesh-free internal geararea will move substantially in a radial direction to a pinion axis 19due to the pressure forces (force resultant) that act on the internalgear 16 in the displacement chamber (pressure chamber) so that toothheads on the low pressure side will seal on account of their mutualabutment. The pin 46 is arranged in bores 47, 48 of the housing parts20, 21. Principally, at least one separate pin 38 (FIG. 1 and FIG. 2) isused as a securing element, being pressed with a first end 39 into abore 40 of the housing part 21 and including a stop 42 at a second end41 to secure the housing part 20 in position. Pin 38 extends exactly aspin 46 in parallel to the pump shaft 12. Further, pin 38 includes acylindrical portion 43 extending through a bore 44 of the stop-sidehousing part 20. Bore 44 has a diameter which is larger compared toportion 43, but smaller compared to the stop 42, with the result of aform-fit securing arrangement. The use of several securing elements,such as the use of two or three pins 38 which are provided at a regularangle α is favorable.

The pump shaft 12 extends through aligning bores of the housing pars 20,21 lined with sliding bearing elements 22, 23. Said sliding bearingelements 22, 23 are preferably press fitted into the bores, the firstsliding bearing element 22 being provided within the first housing part20, while the second sliding bearing element 23 is arranged inside thebore of the second housing part 21. The bearing forces of the slidingbearing element 22 are introduced through the housing part 20 into theaccommodating member 3 in all embodiments. To support the pump shaft 12,the housing part 20 according to FIGS. 3 and 4 is generally bowl-shapedand includes a generally flat bottom 24 with a through-bore 25 in whichthe sliding bearing element 22 is inserted, which supports an end of thepump shaft 12 directly beside the pinion 13. For the introduction offorce into the accommodating member 3, a tubular collar 26 that isintegrally arranged at the disc-shaped bottom 24 is provided and fixedat the accommodating member in the area of a wedged portion 31. In anaxial direction, the housing part 20 abuts with a tubular connectionpiece 49 that embraces the pump components outwards on a step 28. Thebore 7 has several steps and includes a first step 27 that passes overinto a second diameter portion with the second step 28. Also, housingpart 21 is supported on the second step 28 in a fluid-tight fashion bymeans of a sealing element 29. A third diameter portion with a thirdstep 30 accommodates the sliding bearing element 23 so that the bearingforces are introduced into the blind-hole-type end of bore 7. Thehousing part 21 does not participate in the introduction of force intothe accommodating member. This type of construction permits designingthe bore 7 of the accommodating member 3 with comparatively coarsetolerances, while the fine tolerances are related to the pumpcomponents. Another special feature of the embodiment according to FIG.4 involves that pin 46 is designed like pin 38 according to FIG. 1 sothat two functions (safety function, compensation function) arefulfilled by one single component (pin 38).

The embodiment according to FIG. 1 and FIG. 2 differs as follows fromthe embodiment according to FIG. 3 and FIG. 4 described hereinabove. Thehousing parts 20, 21 have the shape of plates and are supported in eachcase with an outside periphery on an inside wall of bore 7 for theintroduction of the bearing forces. For this purpose, the bore 7 ismanufactured in one operation by means of one single tool with a highrate of accuracy.

In contrast to known internal gear pumps, all embodiments have noseparate axial discs for forming the supply channel 9 and the dischargechannel 11 because this function is integrated into the housing parts20, 21. Pinion 13 and internal gear 16 move in an axial direction todirectly abut on the housing parts 20, 21.

All embodiments are identical in that the pivot axis A is also used toposition the second housing part 21 in a circumferential directionrelative to the first housing part 20. After the assembly of the pump inbore 7, a rotation of the housing parts 20, 21 relative to each other isprevented by means of a component, i.e. axis A (pin 38, 46). In theembodiment according to FIG. 3 and FIG. 4, pin 46 is even used toachieve the compensation effect without the need to provide a bore inthe accommodating member to accommodate the axis A. The respectivecomponents are positioned relative to each other already as apre-assembled construction unit.

Further, all embodiments have in common that the first housing part 20with respect to the accommodating member 3 is defined preferably bymeans of axial abutment on a step (27 in FIGS. 1 and 2; 28 in FIGS. 3and 4). The housing part 21 is only accommodated in the stepped bore 7and bears against step 28 in a close sliding fit (transition fit). Thereis no independent attachment.

FIG. 4 displays an elastically biased, needle-shaped spring element 32which is inserted with a first end 33 into a bore 34 of the firsthousing part 20, favorably in a press fit, and engages with a second end35 under elastic deformation (bending) into a bore 36 of the ring 17 inorder to retain it in a defined inactive position. The embodimentaccording to FIG. 1 and FIG. 2 can be equipped with a spring element ofthis type, even if it is not shown in the drawing.

To seal a high-pressure area in relation to a low-pressure area, asealing element 37 is provided in a space 45 between the housing part 20and the pump shaft 12, said sealing element being press fitted into aninside wall of the collar 26 and bearing with one or more sealing lipsagainst the pump shaft 12.

1-10. (canceled)
 11. Motor/pump unit for slip-controlled motor vehiclebrake systems, including an accommodating member for hydraulicallyactive components, an internal gear pump arranged in a bore of theaccommodating member and comprising pump components such as apinion/internal gear combination arranged between two housing parts, thepump components forming a pre-assembled unit including a motor fordriving the internal gear pump, wherein the housing parts are arrangedpreliminarily by at least one securing element in such a fashion thatthe final alignment of the housing parts relative to each other takesplace when the unit is inserted into the accommodating member. 12.Motor/pump unit as claimed in claim 11, wherein the at least onesecuring element connects the housing parts with a relative clearance toeach other, and in that a bore is provided in the accommodating memberfor the alignment of the housing parts in a radial direction. 13.Motor/pump unit as claimed in claim 12, wherein a first housing part isfixed on the accommodating member so as to be undisplaceable in an axialdirection and in a radial direction, and in that the first housing partis provided to lock the pump components in the accommodating member. 14.Motor/pump unit for slip-controlled motor vehicle brake systems,including an accommodating member for hydraulically active components,an internal gear pump arranged in a bore of the accommodating member andcomprising pump components such as a pinion/internal gear combinationarranged between two housing parts, the pump components forming apre-assembled unit including a motor for driving the internal gear pump,and the housing parts are arranged preliminarily by at least onesecuring element in such a fashion that the final alignment of thehousing parts relative to each other takes place when the unit isinserted into the accommodating member wherein a pin with a first end isprovided as a securing element which is press fitted into a bore of oneof the housing parts, and in that the pin includes a second end with astop for securing another housing part in position.
 15. Motor/pump unitas claimed in claim 14, wherein the pin is arranged in parallel to apump shaft.
 16. Motor/pump unit as claimed in claim 14, wherein the pinincludes a cylindrical portion, which extends through a bore of thestop-sided housing part, and in that the bore has a diameter that islarger compared to the cylindrical portion, and in that the diameter issmaller compared to the stop.
 17. Motor/pump unit as claimed in claim14, wherein a maximum of three pins are provided, and in that the pinsare arranged at a regular angle (α) relative to each other. 18.Motor/pump unit for slip-controlled motor vehicle brake systems,including an accommodating member for hydraulically active components,an internal gear pump arranged in a bore of the accommodating member andcomprising pump components such as a pinion/internal gear combinationarranged between two housing parts, the pump components forming apre-assembled unit including a motor for driving the internal gear pump,and the housing parts are arranged preliminarily by at least onesecuring element in such a fashion that the final alignment of thehousing parts relative to each other takes place when the unit isinserted into the accommodating member, wherein an internal gear issupported in a ring, in that ring is arranged in an axial directionbetween the housing parts, said ring being pivotable relative to thehousing parts about a pivot axis (A) that is arranged in parallel to apump shaft.
 19. Motor/pump unit for slip-controlled motor vehicle brakesystems, including an accommodating member for hydraulically activecomponents, an internal gear pump arranged in a bore of theaccommodating member and comprising pump components such as apinion/internal gear combination arranged between two housing parts, thepump components forming a pre-assembled unit including a motor fordriving the internal gear pump, and the housing parts are arrangedpreliminarily by at least one securing element in such a fashion thatthe final alignment of the housing parts relative to each other takesplace when the unit is inserted into the accommodating member, wherein apin is used as pivot axis (A), and in that the pin is supported in boresof the housing parts.
 20. Motor/pump unit as claimed in claim 19,wherein a housing part accommodates an end of a spring element, and inthat another end of the spring element is engaged in a bore of the ring.